The present invention relates to a method of efficiently arraying light emitting devices, and a method of fabricating an image display unit using a mounting method.
The assembly of an image display unit by arraying light emitting devices in a matrix is performed in two manners. For a liquid crystal display (LCD) or a plasma display panel (PDP), the light emitting devices are directly formed on a substrate, and for a light emitting diode display (LED display), single LED packages are arrayed on a substrate. In particular, for an image display unit such as an LCD or PDP, device isolation cannot be performed and accordingly, in general, at the beginning of the production process, devices are formed such as to be spaced from each other with a pitch equivalent to a pixel pitch of the image display unit.
Conversely, for an image display unit such as an LED display, LED chips are packaged by taking out LED chips after dicing, and individually connecting the LED chips to external electrodes by wire-bonding or bump-connection using flip-chip. In this case, before or after packaging, the LED chips are arrayed with a pixel pitch of the image display unit. However, such a pixel pitch is independent from an array pitch of the devices at the time of formation of the devices.
Since an LED (Light Emitting Diode) as a light emitting device is expensive, an image display unit using such LEDs can be produced at a low cost by producing a large number of LEDs from one wafer. Specifically, the cost of an image display unit can be lowered by reducing the size of an LED chip from an ordinary size, about 300 m square to several ten m square, and producing an image display unit by connecting such small-sized LED chips to each other.
When taking out LED chips after the dicing step and individually mounting the LED chips, since each of the LED chips has a micro-size, the step of mounting the LED chips is significantly complicated, to thereby significantly degrade the productivity. Also, when individually mounting LED chips, there occurs a problem associated with positional accuracy, for example, a difficulty in mounting the LED chips with a constant array pitch.